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From: Oleg Nesterov <oleg@redhat.com>
To: Serge Hallyn <serge.hallyn@canonical.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Howells <dhowells@redhat.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	lkml <linux-kernel@vger.kernel.org>,
	richard@nod.at, "Eric W. Biederman" <ebiederm@xmission.com>,
	Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 2/2] creds: __task_cred(current) doesn't need rcu_read_lock_held()
Date: Tue, 20 Sep 2011 17:35:42 +0200	[thread overview]
Message-ID: <20110920153542.GA17731@redhat.com> (raw)
In-Reply-To: <20110920150726.GA6234@peqn>

On 09/20, Serge Hallyn wrote:
>
> Quoting Oleg Nesterov (oleg@redhat.com):
> > Change __task_cred(task) to accept "task == current" without
> > rcu_read_lock_held(). This is what current_cred() currently does,
> > and with this change __task_cred() becomes more flexible/usable.
> >
> > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
>
> So to check whether I've got this straight, the original __task_cred()
> was allowing rcu read lock to not be held for a non-running task, but
> required rcu read lock if task was running?  With these two patches,
> rcu read lock will not be needed if task == current?

Yes.

> If so, then that sounds good to me, and an unconditional rcu_read_lock()
> at wait_task_zombie() seems better than at send_signal()...

Agreed.

Although sometimes I think it would be better to use rcu_dereference_raw()
with a comment in some places.

Oleg.


  reply	other threads:[~2011-09-20 15:40 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-19 21:45 [PATCH] user namespace: make signal.c respect user namespaces Serge E. Hallyn
2011-09-19 21:47 ` [PATCH] user namespace: usb: make usb urbs user namespace aware Serge E. Hallyn
2011-09-20 13:17   ` Oleg Nesterov
2011-09-20 13:33     ` Serge E. Hallyn
2011-09-21  5:01     ` [PATCH] user namespace: usb: make usb urbs user namespace aware (v2) Serge E. Hallyn
2011-09-21 18:31       ` Oleg Nesterov
2011-09-21 19:12         ` Serge E. Hallyn
2011-09-21 19:18           ` Greg KH
2011-09-23  1:27             ` [PATCH resend] " Serge E. Hallyn
2011-09-23 15:48               ` Alan Stern
2011-09-23 16:06                 ` Serge E. Hallyn
2011-09-23 16:21                   ` Alan Stern
2011-09-23 17:22                     ` Serge E. Hallyn
2011-09-23 18:35                       ` Alan Stern
2011-09-20 12:22 ` [PATCH] user namespace: make signal.c respect user namespaces Oleg Nesterov
2011-09-20 12:44   ` Serge E. Hallyn
2011-09-20 13:41     ` Oleg Nesterov
2011-09-20 14:39       ` [PATCH 0/2] (Was: user namespace: make signal.c respect user namespaces) Oleg Nesterov
2011-09-20 14:39         ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check Oleg Nesterov
2011-09-20 15:14           ` drivers/staging/usbip/ abuses task_is_dead/exit_state Oleg Nesterov
2011-09-20 18:38             ` Greg KH
2012-03-06 17:39               ` ping: " Oleg Nesterov
2012-03-06 19:30                 ` Tobias Klauser
2012-03-08 18:57                   ` Oleg Nesterov
2012-03-13 11:45                     ` Tobias Klauser
2012-03-13 18:07                       ` [PATCH] staging: usbip: fix the usage of kthread_stop() Oleg Nesterov
2012-04-01 23:17                         ` Oleg Nesterov
2012-04-02  8:11                           ` Tobias Klauser
2011-09-20 15:28           ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check Paul E. McKenney
2011-09-20 15:40             ` Oleg Nesterov
2011-09-20 15:48               ` Paul E. McKenney
2011-09-20 14:39         ` [PATCH 2/2] creds: __task_cred(current) doesn't need rcu_read_lock_held() Oleg Nesterov
2011-09-20 15:07           ` Serge Hallyn
2011-09-20 15:35             ` Oleg Nesterov [this message]
2011-09-20 16:19         ` David Howells
2011-09-20 16:38           ` Oleg Nesterov
2011-09-20 16:50           ` David Howells
2011-09-20 17:13             ` Oleg Nesterov
2011-09-20 16:27         ` [PATCH 1/2] creds: kill __task_cred()->task_is_dead() check David Howells
2011-09-20 15:39   ` [PATCH] user namespace: make signal.c respect user namespaces Serge Hallyn
2011-09-20 16:24     ` Oleg Nesterov
2011-09-20 16:45       ` Serge E. Hallyn
2011-09-20 18:17         ` Oleg Nesterov
2011-09-21  5:00   ` [PATCH] user namespace: make signal.c respect user namespaces (v2) Serge E. Hallyn
2011-09-20 17:48 ` [PATCH] user namespace: make signal.c respect user namespaces Oleg Nesterov
2011-09-20 18:53   ` Serge E. Hallyn
2011-09-21 17:53     ` Oleg Nesterov
2011-09-22 15:23       ` Serge Hallyn
2011-09-23 16:31       ` Serge E. Hallyn
2011-09-23 17:36         ` Oleg Nesterov
2011-09-23 21:20           ` Serge E. Hallyn
2011-09-24 16:37             ` Oleg Nesterov
2011-09-25 20:17               ` Serge E. Hallyn
2011-09-26 16:06                 ` Oleg Nesterov
2011-09-27 14:28                   ` Serge Hallyn
2011-09-27 14:38                     ` Oleg Nesterov
2011-09-27 15:27                       ` Serge Hallyn
2011-09-27 17:12                         ` Oleg Nesterov
2011-10-04 17:42                   ` Serge E. Hallyn
2011-10-09 19:00                     ` Oleg Nesterov
2011-10-11 13:08                       ` Serge E. Hallyn
2011-10-08 20:02                   ` Serge E. Hallyn
2011-10-09 19:03                     ` Oleg Nesterov

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